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"The repeater is down... again" - 08 November

"The Repeater is Down... Again, one week later"

Some intermittence was noted with the repeater earlier in the day leading up to complete outage around 1130. This was reported to the repeater team who were able to take some troubleshooting steps to determine the system was timed out again. No carriers were noticed by club members in the valley on the input which brought some suspicion. With this report, along with a list of other tasks needing to be done, a trip up the hill was decided to be had to catch the system in the act. KG7RDR, KG7TIR, WD9DWD, and K2RKT arrived in the early afternoon and began checking things out. It was determined that the repeater radios were functioning as expected, but the controller was not receiving appropriate signals. There are two aspects to this, a COS (carrier operated signal or squelch signal) and a TOS (tone operated signal) which will trigger if the input tone of 77.0 is correct. These two signals are presented to the repeater controller which qualifies them and begins repeating if both are present. Due to the design of the radio not being able to sink enough current, a pair of outboard NPN transistors (2N2222) were installed in the DB25 clamshell on the back of the Kenwood repeater radio. These transistors take the small amount of current from the Kenwood TKR-850 repeater auxiliary outputs and trigger the RLC-2 controller by dragging the lines to ground. 

Upon disassembly of the DB25 clamshell some interesting issues with the leads of the COS transistor were noticed. All of the tin and silver coating was flaking off and the solder joint had become unreliable. A 10k resistor was replaced and the transistor leads tinned with solder. After reassembly and reconnection all seemed well for the moment, but some tactical wiggling of the transistors would cause intermittence. The connector was disassembled again at which point it was noted the COS transistor was an older germanium variety in a metal TO-18 package and the insulators had fallen apart resulting in occasional shorting of the emitter to the housing which is at the same potential as the collector. This resulted in the repeater controller being grounded and "seeing" an "active" signal as if someone was keyed up which would time out the system. Fortunately we had a modern silicon replacement on site.

Due to the sun going down we took a detour to do some work on the intertie repeater. A new battery was installed and the tower was climbed to replace the single folded dipole going to Jumpoff. The signal margin on that link was not as high as desired resulting in some hiss on everything from the north. The old yagi had been left on site by the operators of the intertie in anticipation of this. KG7RDR had been asked to install the antenna which was completed in the dark. A new N connector was put on an open LDF4-50 heliax to comply with regulations and the cables were all buttoned up for the winter. This completed, focus was turned back to the K7RCN repeater.

A modern 2N2222 transistor was soldered inside the shell and tests verified everything was stable. For good measure some antioxidant grease was applied to the connectors and the repeater was put back into service. The crew left the site sometime around 20:30 in the cold and dark with everything working.

~KG7RDR